1. Field of the Invention
The invention is directed to valves, specifically, the invention is directed to fluid pulse valves.
2. Background of the Invention
Rotary valves are used in industry for a number of applications like controlling the flow of liquids to molds, regulating the flow of hydraulic fluids to control various machine functions, industrial process control, and controlling fluids which are directed against work pieces. The vast majority of these applications are conducted at low fluid pressures and at either low rotational speeds or through an indexed movement. These applications have been addressed through application of various known fluid regulation valve applications including gate valves, ball valves, butterfly valves, rotating shafts with various void designs and configurations, solenoid actuated valves of various designs, and valves designed with disks with multiple holes to redirect flow streams. These applications are generally acceptable for low speed, low pressure processes, but are not suitable for high speed, high pressure processes.
For example, solenoid valves are effective for regulating fluid flow up to a frequency of approximately 300 Hz at a pressure of up to 200 psi. These limitations are primarily due to the physical design of the solenoid which relies upon the reciprocating motion of magnetic contacts and is therefore subject to significant acceleration and deceleration forces, particularly at higher frequencies. These forces, the resulting jarring action, and the frictional heat generated make these type valves subject to failure at high frequencies of actuation.
Rotary valves employing multiple outlets have been used at frequencies up to 1000 Hz in applications where a low pressure differential between valve inlet and outlet ports is desired. These valves, however, are large and complex and necessarily have significant physical space requirements for the valve and for the appurtenant inlet and outlet piping.
Other types of valves have disadvantages that include: the valve actuation cycle speed (frequency) of the valve is too low, the valve is large and physically complex, the valve creates significant head loss, the valve cannot satisfactorily operate at high inlet pressures, or the valve cannot create the necessary frequency or amplitude of flow perturbation.
In the oil and gas industry, bores are drilled to access sub-surface hydrocarbon-bearing formations. Conventional drilling involves imparting rotation to a drill string at surface, which rotation is transferred to a drill bit mounted on a bottom hole assembly (BHA) at the distal end of the string. However, in directional drilling a downhole drilling motor may be used to impart rotation to the drill bit. In such situations it tends to be more difficult to advance the non-rotating drill string through the drilled bore than is the case when the entire length of drill string is rotating. Furthermore, during use, the drill string often becomes jammed or otherwise unable to continue drilling. Currently the entire drill string must be removed to determine the cause of and fix the problem.
For the foregoing reasons, there is a need for a high-speed, high pressure rotary valve for controlling the flow of a fluid to produce high frequency fluid pulses or perturbations. Further, there is a need for such a valve which is suitable for high pressure applications with minimal head loss through the valve and is easily removable to leave a clear bore without disrupting the entire drill string.